Evapotranspiration (ET), which links water, energy and the carbon cycle in terrestrial ecosystems, is an important eco-hydrological process, especially in arid and semi-arid regions. To determine the crop coefficient (K-c) over a 2-year period for a temperate desert steppe in Inner Mongolia, China, ET was measured using the eddy covariance method and the reference evapotranspiration (ET0) was estimated from site meteorological data. The results showed that the seasonal variation of ET differed on an annual timescale between the 2 consecutive years, exhibiting a multi-peak curve in 2008 and a single peak in 2009. The mean daily K-c values were 0.15 and 0.17 in 2 years, varying from 0.009 to 0.75 in 2008 and from 0.005 to 0.58 in 2009. The 5-day moving average for K-c values was mainly affected by SWC10cm and R-n, and the regression coefficients (R-2) were 58.9 and 69.5%, respectively. These results will aid in making accurate and quantitative assessments of the vulnerability of the sparse vegetation to climate change.